Production of polynitro organic compounds



Patented Jan. 16, 1951 UNITED STATE s PATENT OFFICE PRODUCTION OF POLYNITRO ORGANIC COMPOUNDS William I. Benton, Woodbury, Richard B. Bishop,

Haddonfield, and Edwin M. Nygaard, Woodbury, N. .I., assignors to Socony-Vacuum Oil Company, Incorporate York d, a corporation of New No Drawing. Application March'20, 1947, Serial No.,736,104

6 Claims. (01. 260644) This invention relates to a method of obtaining improved yields of secondary or tertiary polynitro organic compounds from organic compounds containing a lesser number of nitro groups. It will'be specifically described as a method of preparing 2,2-dinitropropane from propane and 2- nitropropane, but is applicable to the preparation of any other secondary or tertiarypolynitro organic compound.

The production of 2,2-dinitropropane from 2- nitropropane and the production of other polynitroparafiins from nitroparaflins having a lesser number of nitro groups has been describedv in United States patent application Serial No.

' 613,713, filed August 30, 1945, by' Edwin M. Ny-

" fromparaffinic hydrocarbons has been described in United States patent application Serial No. 629,001, filed November 15, 1945, by Edwin M. Nygaard et a1. disclosed in this application, parafiins, such as propane, can be converted to mononitro parainns, such as 2-nitropropane, and dinitroparafiins, such as 2.2-dinitropropane, under reaction .conditions similar to those described above.

It has now been found that when a mixture of a mononitroparafiin and its parent paraffinic hydrocarbon is used as the; charge in the process described in United States patent application Serial No. 629,001, supra, alarge andunexpected increase in the efiiciency' of the process results. Specifically, and by way of example only, the nitration of a mixture of Z-nitropropane and propane results in far more" eflicient production of 2,2-dinitropropane and 2-nitropropanethan, can be accomplished by using either 2-nitr0propane or propane alone.

Utilizing this knowledge, a continuous process has been devised which produces notonly an increased yield of 2,2-dinitropropane, for example,

but also 2-nitropropane in suflicient amounts so that it can be recharged into the system along with additional propane and nitrating agent, thereby obviating the necessity of supplying 2- nitropropane from anoutside'source.

In accordance with the present invention, the continuous process for producing polynitro oranic compounds comprises passing a nitro organic compound containing a lesser number of nitro groups than the desired end product, its parent'compound, and a nitrating agent, in the 1 desired proportions, through a stainless steel rebe described in detail hereinafter.

action tube under reaction conditions which will The reactor, if desired, may be packed with an inert material such as glass beads in, order to increase mixing and contact surface area.

The products may thereafter be condensed and separated into individual components. The reaction tube can be immersed into a molten heat transfer salt in order to obtain the desired temperature control. The pressure can be controlled by a pressure regulating valve on the outlet side of the reactor while the feed pumps suitably maintain constant proportions and amounts of the charge materials.

As indicated in the patent applications mentioned above, the preferred nitrating agent is ni- A trio acid in a concentration ranging from forty to 36. In accordance with the process seventy per cent. However, other concentrations of nitric acid and also oxides of nitrogen higher than NO may be used, for example, N02, N203,

N204 and N205.

Some sulphuric acid may be present, in which case nitrosyl sulphuric acid is probably formed, but it is undesirable to have any large .proportion of sulphuric acid present asit tends to oxidize the charge materials before {they have had an opportunity to react with the nitrating agent.

Various molar proportions of the starting nitro compound, parent compound and of nitrating agent may be used. In general, it is preferred to have an excess of nitro compound and parent compound since this tends to control the reaction. Ratios of one-half to one mole of nitric acid to one mole total of parent compound plus pnitro compound are satisfactory. We have found 1 that as the proportion of nitric acid in the charge is increased, explosions are likely to occur. The ratio of parent compound to nitro compound preferably is regulated so a'sto produce a conprobable formation of amines.

stant amount of the starting nitroparafiin for recycling. This permits the process to be operated so as to produce the desired polynitro compound as the only product.

It has been found desirable to use as a. charge mixture of nitro compound and parent compound, a mixture which contains between about 0.25 and about 4.0 moles of the parent compound per mole of the nitro-.compound. Preferably, the mixture contains between about"0.5 and about-2.0- moles of parent compound per mole of nitro compound.

As pointed out in the preceding paragraph, the use of a molar excess of the parenttcompound and/or of the nitro compound gives better control of the reaction. It has been found that theuse of With an inert solid material in order to effect other materials, such as water,:nitrogen, :carbon dioxide, and the like, as.di1uents, ,likewiseprovides better control of the reaction. Water is desirable when used in proportions of from about 10 to about 80 mole per cent, based on the sum of the molar quantities of the-parent compound, nitro compound, nitric acid and water. Water is a product of the reaction and therefore, .'to;a certain extent, dilution of the 'nitric acid when the latter is used as thenitratingagent.is.,not detrimental in a recycle or,a continuonsprocess.

.In this connection, when1'O0 nitric acidis. used, the amounts and yields of mononitroand. .dinitro compounds obtained are,gener.ally lower .than when dilute nitric acid 'is.employ ed.. ,Forty to seventyper cent acid is thereforepreferable.

Temperature is a criticallfactorinthe process since at temperatures. of beloweabout. 15.0". C. no appreciablereaction takes-place, while .at temperatures of above. about 250" ,C. decomposition 'of the, product and mild explosionsbegin. Violent explosions occur when the temperatures ,reach 260 300" C. Atthese temperatures,-the,product.

obtained is .alkalinelin reaction, indicating the Thetemperature at which. explosions areencounteredis dependent on other variables, such asmolar; ratio andspace velocity. Accordingly,.the,range .of variation :of temperature will vary for any. given setof operating conditions. 'is' from about 150 C..toabout 230 .C.

The preferredtemperature range Pressure is another. essential consideration-in th process. compounds.- are formed. However, as..the pressure isincrease'd above about 150 pounds per square inch, the, f ormationof dinitro vcompounds begins.

Generally the .rate -cf increasein the. .amountz of conversionper .passincreases .with increases in pressure up to about .1200 pounds pensquareinch. Above aboutl200 pounds per, square inchtherate of xincreasejjfalls ofi. .Thus, whileincreasing the pressure from about 300 pounds to 900 pounds per square inch might. increase .the conversion 5 per cent, increasing .the,pressure from l200..to 1800 pounds..per square inchwould increasetheconversion only'2.per ,cent. Pressures in the range of about.200,to.2500.pounds per. squareinch probably include all that can be consideredpractical, whereas pressures of ab,o,ut..80,0e1-20.0 pounds-per .squareinch .are preferred. One.,method.,of..ob-

taining the ,desiredtemperature. control, is to, circulate heat transfer. salt. around. and. through. the

between about.0.5. and about 2.5.

"The reaction chamber is preferably ;.made pf,

At,atmospheric..pressure.no dinitro better mixing and contacting of the reactants.

';We have found, for example, that a stainless steel reactor packedwith glass beads is satisfac- Jtoryforthepurposes of the present invention. However, packing is not essential.

In carrying out the process of our invention, the reactants may be metered by individual pumps, mixed cold, preheated, and the mixture charged into the reactor. When, for example, per cent nitric acid and Z-nitropropane are among'the reactants used in the process, they may be mixed in the .desired molar proportions and then umped using a: single pump. -When .the.reactants,..or some of them, are not mutually miscible, separatepumps must-be used.

Whennitric acid is used as the nitrating agent, vithas beenfoundeonvenient, in small scale tests, to-pumpitbydisplacement with oil. When this ,.,is.f.done it is desirable.thatthe-oilshould besa .highlyparaffinic or naphthenic oil which will not react with the nitric acid. When NZOzlS used as the nitratingagent, the oil-should be in 'con- ,tact with the NzOifonas short-a timeaspossible, otherwise violent'reaction mayresult. In larger ,scale .operations, ,the .nitrating agent may -.be pumped ,or metered directly. Precautions should be takento prevent any possibility ofthe nitrating ,agent .mixingwith thehydrocarbonsin the system from which .the hydrocarbons "arm-supplied and-to .this=end. an excess of hydrocarbons should .be maintained .in the charging system whilethepperation isbeing started and adjusted.

' .Check valves cannbe-used toprevent any-pos- .s'ibilitybf -the .nitric acid backing up into --the hydrocarbon. supplyv line.

Further details and advantages .of this inven- ,tion .willbeapparent from .thefollowing specific examples.

AlLruns were made. at.,.a temperature. of A00 (20,4 C.) .andata pressure of9l0 poundsper square inch. ,Seventy .per. cent nitric acid was .used and the space velocity v.was adjusted torgive approximatelypqual reaction. When propaneis used it wasffounddesirable to-use.a molarexcess of hydrocarbon-inorder to ,control the re- .action; thischangedthe spacevelocity slightly. For. convenience, the operating. conditions of each run are set 'forthin flableI.

.Table I Moles 01' 2- ".Moles of 11 w g gorg itt d? Run 'Material space Pane an 6 divided 7N0. Charged 'IVlocity' by g by'ni oles by moles of 2-nitr0- of 553 nitric acid propane 1 ,2-nitropropane; ..1.;0 ,1.0 1.5 propane 2:0 1.5 1.5 3, ;2-nitropropane +propane 1 1 3 3.0 1.5 l. 5

1 When propane ,is employed, it is. desirable .to use .an .exccss-of propane-and a high: space-velocity in order to obtain comparable rresulta- The conversion per pass to nitro derivatives obtained in these runs are set forth in Table II.

By operating in accordance with Run N0. 3, separating the 2-nitropropane and recycling it, an excess of 2-nitropropane gradually is built up in the system because more 2-nitropropane is formed than is converted to 2,2-dinitropropar1e. However, by adjusting the molar ratio of the charge materials, 1. e., by reducing the amount of propane charged, this can be prevented and the process operated continuously with only propane and nitric acid charged into the system and only 2,2-dinitropropane and water produced by it.

Although the process of this invention is peculiarly applicable to the preparation of 2,2- dinitropropane, it can also be applied to the formation of polynitroparafins and polynitrocycloparaffins, using paraflins and cycloparaflins as charge materials, such as, for example, butane,

pentanes, hexanes, neohexane, 2,3-dimethylbutane and cyclohexane.

The process of this invention may be made continuous by cooling the reaction mixture as it comes from the reaction zone, thus separating the oxides of nitrogen and unreacted propane, for example, from the liquid products. The liquid products may be separated into a nitric acid layer and a hydrocarbon layer. The hydrocarbon layer may then be distilled to recover and separate the 2-nitropropane and 2,2-dinitropropane. The 2-nitropropane may then be recycled to the process. The oxides of nitrogen may be reconverted to nitric acid and recycled along with the recovered nitric acid and propane. Additional nitric acid and propane will, of course. be added to maintain continuous operation. Numerous possible variations andmodifications of such a continuous process will be apparent to those skilled in the art.

What is claimed is:

1. The process of preparing 2,2-dinitropropane that comprises reacting a mixture of 2-nitropropane and propane with a nitrating agent at a temperature between about 150 C. and about 250 C., at a pressure in excess of about 150 pounds per square inch and at a space velocity in excess of about 0.1.

2. A process of preparing a polynitroparafiin having at least three carbon atoms, and characterized by the attachment of at least two nitro groups to other than primary carbon atoms, which comprises reacting a mixture of a nitroparafiin having at least one less nitro group than the said polynitroparafi'in, and a paraffinic hydrocarbon having the same number of carbon atoms and the same carbon atom structural configuration as the said nitroparafiin, with a nitrating agent, at a temperature of from about 150 C. to about 250 C., at a pressure in excess of about 150 pounds per square inch and with a space velocity in excess of about 0.1, said nitroparafiin reactant having at least three carbon atoms and 6 being characterized by the attachment of its nitro groups to other than primary carbon atoms and being further characterized by the attachment of at least one hydrogen atom to other than a primary carbon atom.

3. A process for preparing a polynitroparaffin having at least 3 carbon atoms and not more than 5 carbon atoms in the molecule, and characterized by the attachment of at least 2 nitro groups to other than primary carbon atoms, which comprises reacting a mixture of a nitroparaflin having at 1east one less nitro group than the said polynitroparafiin, and a paraffinic hydrocarbon having the same number of carbon atoms and the same carbon atom structural configuration as the said nitroparafiin, with a nitrating agent, at a temperature of from about C. to about 250 C. and at a pressure in excess of about 150 pounds per square inch, while moving the reactant mixture through a reaction zone at a space velocity in excess of 0.1, said nitroparafiln reactant having at least 3 carbon atoms and not more than 5 carbon atoms in the molecule and being characterized by the attachment of its nitro groups to other than primary carbon atoms and being further characterized by the attachment of at least one hydrogen atom to other than a primary carbon atom.

4. A process for the preparation of a gem-dinitroparaffin having from 3 to 5 carbon atoms characterized by the attachment of the two nitro groups to a secondary carbon atom, which comprises: reacting a mixture of a'mononitroparaffln having from 3 to 5 carbon atoms and having the nitro group attached to a, secondary carbon atom, and a parafiinic hydrocarbon having the same number of carbon atoms and the same carbon atom structural configuration as the said mononitro araffin, with a nitrating agent at a temperature from about 150 C. to about 250 C. at an elevated pressure in excess of about 150 pounds per square inch, while moving the reactants through a reaction zone at a space velocity in excess of about 0.1.

5. A process of preparing 2,2-dinitropropane which comprises reacting a mixture of 2-nitropro ane and propane with nitric acid at a temperature between about 150 C. and about 250 C., at an elevated pressure of from about 800 to about 1,200 pounds per souare inch and with a space velocity between about 0.5 and about 2.5.

6. A process of preparing 2,2-dinitropropane which comprises reacting a mixture of 2-nitropropane and propane in the ratio of from about 0.25 to about 4 mols of propane to per mol of 2- nitropropane with nitric acid at a temperature between about 150 C. and about 250 C., at an elevated pressure of from about 800 to about 1,200 pounds per square inch and with a space velocity between about 0.5 and about 2.5.

WILLIAM I. DENTON. RICHARD B. BISHOP. EDWIN M. NYGAARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,382,241 Levy Aug. 14, 1945 2,394,315 Levy Feb. 5, 1946 2,418,241 Stengel et al Apr. 1, 1947 2,425,367 Denton et al Aug. 12, 1947 

2. A PROCESS OF PREPARING A POLYNITROPARAFFIN HAVING AT LEAST THREE CARBON ATOMS, AND CHARACTERIZED BY THE ATTACHMENT OF AT LEAST TWO NITRO GROUPS TO OTHER THAN PRIMARY CARBON ATOMS, WHICH COMPRISES REACTING A MIXTURE OF A NITROPARAFFIN HAVING AT LEAST ONE LESS NITRO GROUP THAN THE SAID POLYNITROPARAFFIN, AND A PARAFFINIC HYDROCARBON HAVING THE SAME CARBON ATOM STRUCTURAL CONATOMS AND THE SAME CARBON ATOM STRUCTURAL CONFIGURATION AS THE SAID NITROPARAFFIN, WITH A NITRATING AGENT, AT A TEMPERATURE OF FROM ABOUT 150* C. TO ABOUT 250* C., AT A PRESSURE IN EXCESS OF ABOUT 150 POUNDS PER SQUARE INCH AND WITH A SPACE VELOCITY IN EXCESS OF ABOUT 0.1, SAID NITROPARAFFIN REACTANT HAVING AT LEAST THREE CARBON ATOMS AND BEING CHARACTERIZED BY THE ATTACHMENT OF ITS NITRO GROUPS TO OTHER THAN PRIMARY CARBON ATOMS AND BEING FURTHER CHARACTERIZED BY THE ATTACHMENT OF AT LEAST ONE HYDROGEN ATOM TO OTHER THAN A PRIMARY CARBON ATOMS. 